The utility model relates to an unpowered scum scraping and collecting device which comprises a working bridge, a connecting rod, a connecting plate, a scraping arm and a scraper, wherein a vertical truss is fixedly connected below the working bridge; one end of the scraping arm is movably connected to the truss, and the other end of the scraping arm is movably connected with the scraping plate; the upper end of the connecting plate is movably connected with the bottom of the working bridge, the lower end of the connecting plate is movably connected with one end of the connecting rod, the other end of the connecting rod is movably connected to the truss, and the connecting rod is arranged below the scraping arm; a recess is arranged at the middle part of the connecting plate so as to form a hook, and a lifting lug corresponding to the recess position is arranged on the scraping arm; and a positioning roller is also arranged at the middle part of the connecting plate below the recess, and the scraping arm is arranged above the positioning roller and can move between the positioning roller and the recess. With the adoption of the utility model, when the scraping arm moves to the recess position, the lifting lug is locked into the recess. The unpowered scum scraping device has the advantages of convenience in manufacture, low cost, simpleness in installation, stabilization in equipment motion and long service life without the power and noises.